without spider: watch station

There are several methods to reach the bomb slot, explained below. For methods to reach the Sentinel's Path door, see the notes at the bottom.

The original method uses the rezbit at the back. Stay by it until it makes a shield. Space jump on it, then to the nearby spider track (must land near the edge, as it's the only part you can stand on). Space jump on top of the same track, then to the next highest one.

With your back to the bomb slot, jump back and slightly to the right. At the peak of the jump (or a little after), use your second jump and only move back this time. Quickly press X after this and you should trigger an instant morph, where the game puts you in morph ball mode with no animation.

The alternate method doesn't need a rezbit. In front of the door leading to Grand Abyss, ghetto jump off either wall to reach a ledge directly above. Space jump to (or past) the blue window in the corner. Go along this invisible ledge until you're stopped by something,
then space jump out to the lowest track. The alternate method is the same from here.

Notes:

The lowest track can also be reached with a bs jump (2bj/3bj). Remember to land near the track's edge.

If you're just trying to reach Sentinel's Path without the spider ball, there are at least four ways (see the bottom videos). You can maneuver along the track seperating Sentinel's Path from Watch Station, but it's also possible to just scan dash or roll jump the gap. The fourth method is to ride one of the revolving platforms until it's near the ledge, then space jump at it (you should be put on the ledge after falling if you bump against it).